Topic: passageway from air screw to emulsifier tube?, loose jet ?'s

[patpollin]

I'm cleaning my '76 CB550K carbs before this season, and while I cleaned them last year the bike ran rich all season so I'm going through them again to see if I missed anything.  I'm reverting back to original needle jets and air screws.  My emulsifiers are out and very clean , and I decided to make sure they were recieving air as they should be.
this is my main concern:  do the emulsifiers recieve air from the air screw?  Spraying brake parts cleaner into the air screw opening, it comes out of the idle jet threads, the idle jet opening in the carb throat, and through a small hole in the air horn  -- there is no flow from the air screw to the mainjet/emulsifier passageway --  is this a problem?  I have tried forcing mechanic wire from the air screw opening towards the emulsifiers but it doesn't go through, either it is super clogged or there is not meant to be a thru-way.   a clogged port would certainly cause poor combustion and efficiency.  I have checked the brass fitting in the air horn which leads to the emulsifier and all are clear.   

a second concern is on the looseness of the (push in) main jet in its holder.  one carb the jet doesn't stay in on its own.  the body has lost enough material to oxidation to let the jet just fall out.  It is not so bad that I can see past the jet or jet oring, but I know this can lead to fuel leaking around the outside of the jet causing rich issues.   does anyone have a fix for this?   Maybe some JB weld on the inner bore of the main orifice would tighten up the fitting. 

thanks for the help!   

[TwoTired]

There are two air jets at the inlet to the carbs, one feeds the slow circuit, and the other feed the emulsion tubes.  Look for a hole at the venturi ramp on the inlet.  That's the main emulsifier jet.

The main jet needs a good seal between carb body and jet.  But, the oring is not the retaining mechanism.  The leaf springs braced against the installed bowl do that job.

If you have lost enough carb body material that the held in jet won't allow the oring to seal, that's a problem requiring correction.


Cheers,

[patpollin]

thanks for the reply Twotired-    my two air inlets for the main and idle circuits are clear,  but now I am wondering what exactly does the air screw do?  and how come it is only connected to the idle circuit?   

[TwoTired]

  The idle circuit is also called the slow circuit and also the Pilot circuit.  The Air screw primarily effects the Slow/Idle/Pilot mixture ratio. 

However, the Slow/Idle/Pilot system does not shut off when the throttle valve dominates.  So, it does have some minor contribution there, as well.  To adjust the throttle valve mixture ratio, you raise or lower the throttle valve needle, or change the taper profile.

The emulsion tube bleed holes (number and size) can also be changed to effect the throttle valve mixtures.

Cheers,